Evrim Yazgin
Cosmos science journalist
NASA’s James Webb Space Telescope (JWST) has observed swirling clouds of grit on a planet in a star system 40 lightyears outside our solar system.
Researchers analysing data from the JWST of the atmosphere of planet VHS 1256 b, have proven that the clouds are made up of silicate particles ranging from grain-sized to dust-sized specks.
With a name like VHS, it’s no wonder the planet is grainy.
The gas giant has a 22-hour day and its atmosphere is dynamic. The churning storms on VHS 1256 b reach temperatures of 830°C. Hotter material rises while colder material is pushed down, seeing the planet’s atmosphere constantly rising, mixing and moving. These changes are observed by the JWST scientists as changes in brightness.
So dramatic are these changes that VHS 1256 b is the most variable planetary-mass object known to date, according to NASA’s press release.
The researchers also found water, methane and carbon monoxide as well as traces of carbon dioxide – the largest number of molecules at once on a planet outside our solar system.
VHS 1256 b orbits two stars. A year on the planet is 10,000 years on Earth.
Researchers were able to analyse the infrared spectra of the planet directly because it orbits its central stars at such a great distance.
“VHS 1256 b is about four times farther from its stars than Pluto is from our Sun, which makes it a great target for Webb,” says lead author of a paper in Astrophysical Journal Letters on the research, Dr Brittany Miles from the University of Arizona. “That means the planet’s light is not mixed with light from its stars.”
JWST spotted another gas giant which has been dubbed a “hot Jupiter”.
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The exoplanet, HD149026b (also called Smertrios), is super-abundant in heavier elements carbon and oxygen. This is unusual for a planet of its size.
“It’s the mass of Saturn, but its atmosphere seems to have as much as 27 times the amount of heavy elements relative to its hydrogen and helium that we find in Saturn,” says Cornell University professor Jonathan Lunine, co-author of a study on the planet published in Nature.
“It appears that every giant planet is different, and we’re starting to see those differences thanks to JWST.”
Smertrios is also strange because it has a high ratio of carbon to oxygen. This may seem suggest suitability for carbon-based life like ourselves, but a high carbon-oxygen ratio actually means much less water on the planet or in the planetary system. This would be a problem for life as we know it.
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But JWST has made observations of another exoplanet which showed promise for habitability but the observations show that this rocky planet has its own problems.
TRAPPIST-1 b is slightly larger than Earth and orbits a cool red dwarf star around a hundred times closer than we orbit our sun. The TRAPPIST system is around 40 lightyears from Earth.
JWST allowed astronomers for the first time to directly measure the temperature of an exoplanet by analysing the light given off by the planet itself. JWST’s Mid-Infrared Instrument (MIRI) was able to detect and examine the heat energy given off in the form of infrared light.
The result showed that the planet’s dayside has a temperature of roughly 230°C. This suggests that its atmosphere has been stripped away, probably by the very active star. Not a good sign for habitability, but an advance in our ability to study these planets outside our solar system.
“This is the first time we can detect the emission from a rocky, temperate planet. It’s a really important step in the story of discovering exoplanets,” says Dr Pierre-Olivier Lagage from the Atomic Energy Commission (CEA) in France and co-author of a paper on the analysis in Nature.